Code:
menu status {
  $iif($group(#locking).status == off,Lock,Unlock) : $iif($group(#locking).status == off,.enable #locking,.disable #locking)
}
#locking off
On *:INPUT:[color:red]#channel[/color]: echo -a *** Locked | halt
#locking end

Replace #channel with the name of the channel that you wish to be able to lock.